Helper T cells Flashcards
Naive T cells differentiate in the lymph nodes via costimulation from antigen on MHC complex into CD4+ Helper T cells.
Helper T cells can then do 2 things what are they?
They can either leave lymph nodes to fight infection OR they join with B cells to form the Germinal Center reaction to make antibodies
Naive T cells differentiate in the lymph nodes via costimulation from antigen on MHC complex into CD4+ Helper T cells.
Helper T cells can then do 2 things what are they?
They can either leave lymph nodes to fight infection migrate thru blood vessel to infected tissue site OR they join with B cells to form the Germinal Center reaction to make antibodies
After Helper T cells differentiate in the lmyph node and travel to site of infected tissue, they use similar procceses as innate inflammation to get out of blood and into the tissue. When in the tissue, DCs and macrophages can take up antigen and present it on their surface via MHC to the heper T cell. How do they respond?
T helper cells recognize the microbial antigen and secrete cytokines that work on other immune cells such as macrophages, DCs, and neutrophils that kill the microbes.
so helper cell really comes in to recognize microbe, release cytokines that tell other immune cells to kill it
- Different Th subsets secrete distinct cytokines that can activate immune responses; these immune responses are specific to different classes of microbes.
Helper T cells can perform their effector functions in multiple different locations. What immune function is likely to be activated by helper T cells in secondary lymphoid organs?
the germinal center reaction
TH1 makes what kind of cytokines? and what is their function?
interferon gamma IFNγ
function: to activate macrophages that can kill intracellular microbes
TH1 cell binds to antigen presented on MHC on macrophage with microbe in it
* CD40L (on TH1) & CD40 bind along with IFN gamma to its receptor to signal killing of microbe in the macrophage
too much macrophage activation could lead to TH1 associated chronic inflammation + autoimmune disease
TH2 cells make what kind of cytokines? what is their function?
IL-4, IL-5, & IL-13 (interlukin)
function: activate eosinophils and gut tissue to expel & kill worms (intestinal parasites)
TH2 binds to antigen (worm peptide) presented to it on MHC on antigen presenting cell - signals interlukin production
IL-5 -> activator of eosinophils (good at worm killing by releasing granules that kill)
IL-4 & IL-13 -> both work on gut, increase mucus production & gut motility for worm expulsion
TH2 cells bad side: allergic disease -asthma, hives, hay fever all related to these cytokines
TH17 cells make what kind of cytokine? what is their function?
IL-17
function: induces acute inflammation leading to production of defensins to fend off extracellular microbes
TH17 cells good for defense against extracellular microbes like fungi, candida, bacteria like staphlocci
APC take up microbe & present to TH17 cell
which secretes IL-17
IL-17 will activate endothelial cells - recruitment of neutrophils & monocytes (innate response)
& it will work on macrophages & neutophils to kill microbes
& it will work on epithelial cells to produce defensins that go out into lumen to kill microbes
TH17 cells can be dangerous - tissue damage - chronic inflammatory diseases autoimmunes
Excessive activation of TH1 cells can lead to …
Granulomas
- happens with intracellular microbes
- made up of alot of macrophages with a rim of T helper cells
- can cause tissue damage, swelling
seen in chrons disease
Excessive activation of Th17 cells can lead to …
inflammation and tissue damage
- happens with extracellular microbes
ex: multiple sclerosis and IBD (ulcerative colitis)
